Radiation risk in home construction materials

NUCLEAR and radiation experts are cautioning the public over potential hazards posed by naturally-occurring radioactive elements in construction materials.

Commonly found in materials naturally sourced from earth, uranium and thorium are Naturally Occurring Radioactive Materials (NORM) often found in bricks, cement blocks, granite, marble or glazed tiles used in the construction of homes.

The two elements (uranium and thorium) undergo a natural decaying process to form other harmful elements and emit several types of radiation, particularly alpha, beta or gamma rays.

Atomic Energy Licensing Board (AELB) director-general Hamrah Mohd Ali, in an exclusive interview with the New Straits Times, cautioned that excessive exposure to these rays could damage human tissue and cells, and cause health issues or death.

The degree of health risks for those exposed to these types of radiation, he said, depended on the levels and duration of exposure.

He said the risk of excessive exposure could be reduced by minimising direct contact with NORM, including wallpaper, plastic or wooden flooring for protection and in the case of gamma, lead.

“Materials traced to natural materials like brick, mosaic, granite or cement blocks… even toilet bowls, contain radioactive materials... There is no way for us to run away from them.

“The levels of radiation vary depending on the origin of the materials.

“For example, mosaic from Kerala, India, may have higher radiation levels than those from the domestic market because the earth in Kerala has higher natural background radiation.

“Exposure to radiation can have long-term, short-term or acute effects...

“We must be careful with the long-term effects because it can slowly kill us even though we may not realise it.”

Hamrah said the types of radiation emitted from radionuclides would also determine the severity of the health effects on those exposed to it.

“Different rays affect us differently. For example, although alpha rays can be blocked using things like a piece of paper, it could cause a lot more damage on a surface, compared with beta, which has smaller particles.

“Since alpha’s particles are bigger, they will affect a wider area when it enters the human body, including through wounds, inhalation or contaminated food.

“For example, if you knead dough directly on top of a chipped granite table top, you will not notice particles containing NORM attaching to it.

“When you consume it, these radioactive materials will enter your body... some might exit through the excretion process, but the rest will continuously emit rays that will kill your cells.”

He said the International Atomic Energy Agency had set 10 microsievert as the “acceptable” yearly “dose limit” to radiation absorption.

The “legal effective dosage” limit or level of radiation reading among the public should be no more than one milisievert a year.

Hamrah, however, cautioned about possible “unknown” effects, even with the most minimal exposure.

“Although the ‘acceptable’ dose has been set at one milisievert per year, those working in the radioactive and nuclear industry are ‘allowed’ to be exposed to up to 20 milisievert per year... This is on top of the background reading.

“But, there is no study that can say for sure that if you receive below one milisievert, you will not be affected,” he said, adding that children would be more sensitive to radiation as their immune systems were not fully developed.

He said apart from the dangers of being exposed to lethal radiation, uranium and thorium also produced radon and thoron, which are also lethal gases.

Radon, a colourless and odourless radioactive gas, is known as the second leading cause of lung cancer in the United States, with an estimated 20,000 deaths a year.

Hamrah cautioned that having more sources containing radioactive materials in a confined area would increase the level of these naturally-produced radioactive gases.

“Uranium and thorium in consumer products will continue to decay, releasing radon and thoron that will accumulate in confined areas.

“Radon in the air will break down into tiny radioactive elements (radon progeny) that will be lodged in the lining of the lungs. It will then release radiation, which can lead to cancer.

“The production of radon and thoron is continuous… meaning, if your house contains more materials that emit radiation, the reading may be higher compared with houses made of wood or with wooden flooring or roofing.”

The US Environmental Protection Agency recommends that radon readings are brought to below four picocuries per litre (pCi/L), although there is no “safe levels” for radon and thoron.

Hamrah shared with NST readers how to manage the gases: make sure your homes are well ventilated. It helps to “dilute” them.

“It is important for homes to have good ventilation. Open the windows, turn on the fan, as this will help remove the gases,” he said, adding that radon would remain in a confined area for four days before it dissipated.

As these gases are continually produced, good air circulation will help channel them out of confined areas.

AELB, Hamrah said, did not monitor the NORM level in soil or imported construction materials.

“The public can lodge a report with the agency if they suspect that the level of radon in their house is high, and we can help them verify it.

“We don’t monitor construction materials, including those from other countries, because Malaysian homes are usually well-ventilated.

“Radon is a huge concern in countries with four seasons because when it is cold, people will shut doors and windows, leaving no room for the air to flow out.

“We will take action if we receive any reports.”

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Uranium and thorium are Naturally Occurring Radioactive Materials often found in bricks, cement blocks, granite, marble or glazed tiles used in the construction of homes. FILE PIC